Not applicable.
Arsenic is one of the most abundant and widely distributed anthropogenic pollutants in many contaminated sites, and can be a significant source of poisoning in agricultural workers, smelters, miners, and chemical plant workers. Moreover, arsenic poisoning due to contamination of drinking water affects thousands of people worldwide. The common method of removing arsenic from water uses chlorine or ozone, and the waste products from such methods are harmful to people.
The chemistry of arsenic is very complex. While some forms of arsenic become tightly bound to surrounding matter, one of the more toxic forms, arsenite, is also the most mobile. For example, arsenite (AsIII) is more toxic than arsenate (AsV) and arsenite is more mobile in the environment than arsenate. Cullen, W. R., Reimer, K. J. Chem. Rev. 1989, 89, 713-764. In general oxidized forms of arsenic tend to be less mobile in, and easier to remove from, the environment. Thus, it is desirable to convert arsenite to arsenate.
The oxidation of arsenite to arsenate in the absence of catalyst is kinetically inhibited. Wilke and Hering reported that certain microorganisms may be able to catalyze the oxidization of arsenite to arsenate at 25xc2x0 C. Wilkie, J. A., Hering, J. G. Rapid Oxidation of Geothermal Arsenic (III) in Streamwaters of the Eastern Sierra Nevada, Environ. Sci. Tehnol. 1998, 32, 657-662. However, the identity of the microorganisms in Wilke and Hering are not known. Id. Several microorganisms are known to be able to oxidize arsenite. These microorganisms include heterotrophs Pseudomonas putida and Alcaligenes faecalis as well as the chemolithoautotrophic arsenite-oxidizers Pseudomonas arsenitoxidans and xe2x80x9cNT-26.xe2x80x9d Turner., A. W. Aust. J. Biol. Sci. 1954, 7, 452-478.; Osborne, F. H., Ehrlich, H. L. J. Appl. Bacteriol. 1976, 41, 295-305.; Ilyaletdinov, A. N., Abrashitova, S. A. Mikrobiologiya 1981, 50, 197-204; Santini, J. M., Sly, L. I; Schnagl, R. D., Macy, J. M. Appl. Environ. Microbiol. 2000, 66, 92-97.
Arsenic is a common constituent of geothermal fluids with typical concentrations of 1-10 mg Lxe2x88x921. Ballantyne, J. M., Moore, J. N. Geochim. Cosmochim. Acta 1988, 52, 475-483. As a result, levels of arsenic are often elevated in surface waters and aquifiers surrounding hot springs. Welch, A. H., Westjohn, D. B., Helsel, D. R., Wanty, R. B. Ground Water 2000, 38, 589-604. For example, at Yellowstone National park, over 100,000 kg of geothermally-derived arsenic is estimated to leave the western boundary each year, affecting water quality within a large region. Nimick, D. A., Moore, J. N. Dalby, C. E., Savka, M. W. Water Resour. Res. 1998, 34, 3051-3067. Stauffer, Jenne and Ball reported that rapid arsenite oxidation at high temperature was observed in the drainage of the Azure Hot Spring of Yellowstone but did not explain why. Stauffer, R. E., Jenne, E. A., Ball, J. W. Chemical Studies of Selected Trace Elements in Hot-Spring Drainages of Yellowstone National Park, 1980, Geological Survey Professional Paper1044-F.
Thermus species bacteria are Gram-negative aerobic rods found in warm waters such as hot springs, hot water tanks and thermally polluted waters. The Thermus species have been studied extensively in pursuit of novel enzymes and biochemical pathways for industrial applications. Alfredsson, G. A., Kristjansson, J. K. In Thermus species, Sharp, R., Williams, R. Eds., Plenum: New York, 1995; Chapter 2. For example, the Taq enzyme used in polymerase chain reaction was first isolated from Thermus aquaticus. So far, no information exists regarding Thermus species"" interaction with arsenic-rich fluids.
The present invention is summarized in that bacteria of a Thermus species can be used to convert arsenite to arsenate. An arsenic contaminated source containing arsenite can be detoxified by incubating bacteria of a Thermus species in the source at a temperature and under conditions in which the bacteria can convert at least some of the arsenite to arsenate.
It is an object of the present invention to detoxify arsenic using microorganisms.
It is another object of the present invention to detoxify arsenic with microorganisms at a relatively high temperature.
It is an advantage of the present invention that no harmful products are generated through the arsenic detoxification process.
Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying claims and drawings.